The present invention relates to tracheostomy tubes having an outer cannula and a removable inner cannula, and, in particular, to a tracheostomy tube having a disposable inner cannula.
Tracheostomy tubes have been used for some time to provide a bypass supply of air or mixture of gases to a patient having an obstruction in the larynx or the pharynx areas of the throat. The distal end of the tracheostomy tube is inserted into the trachea through an incision in the patient's neck below the obstructed area. The proximal end of the tube remains outside the trachea in communication with ambient air to permit passage of such air into the trachea. This proximal end of the tube can also be attached to a respiratory device to assist the patient's breathing or to anesthesia equipment for passing anesthetic gas to the patient prior to surgery.
While thus in place within the patient's trachea, a tracheostomy tube can sometimes become partially or completely obstructed by accumulations of mucus or completely obstructed by accumulations of mucus or phlegm. U.S. Pat. No. 3,693,624 to Shiley et al, assigned to Shiley, Inc., assignee of the present invention, discloses and claims a tracheostomy tube which allows such obstructions to be cleared without causing pain and irritation to the patient, this invention providing an outer cannula, which remains in place in the trachea, and a removable inner cannula, which serves as an inner lining of the outer cannula. Thus, to clear the passageway of the tracheostomy tube, the inner cannula can be removed, cleaned, and then replaced.
An important feature of lined tracheostomy tubes, which insures adequate cleaning, is that the inner cannula runs the entire length of the outer cannula. For example, if the distal tip of the inner cannula were to terminate within the bore of the outer cannula, mucus could accumulate on and adhere to the unlined portion of the interior surface of the outer cannula, obstructing the air passage of the tube and requiring its complete removal for cleaning. At the same time, however, the inner cannula should not extend substantially beyond the outer cannula, since removal and insertion of a protruding inner cannula could cause abrasion of the trachea and damage to the delicate cilia along the inner tracheal wall. Thus, the overall length of such removable inner cannulae must be carefully controlled.
It is also important in such two-part, lined tracheostomy tubes that an adequate air seal be maintained between the inner and outer cannulae so that respiration pressure from an artificial respiration machine is not lost by leakage. One prior method for producing such an air seal at the proximal end of a tracheostomy tube is disclosed in U.S. Pat. No. 4,009,720 to Crandall, entitled "Wedge Seal for a Tracheotomy Tube" assigned to Shiley, Inc.